The Polygraph Lie Detector

摘要

The polygraph measures a person's physiological responses while they are being interviewed: blood pressure, breathing rate, pulse, electrical conductivity of the skin. The subject sits in a chair and has various electrodes and sensors strapped to his chest, middle, arms and fingers. The idea is to determine whether he is more aroused emotionally by certain questions than others. Interviewers use several techniques to determine this. The standard is called the Control Question Test, in which the subject is first asked general questions about his honesty not relevant to the crime - for example: "During the first 18 years of your life, did you ever take something that wasn't yours?" or "Have you ever told a lie to get out of trouble?" These seemingly irrelevant questions are designed so that an innocent person will be more troubled by them than by questions relevant to the crime, whereas a guilty person will react more strongly to questions about the crime.